Association of life-course stressful life events with later-life intrinsic capacity: A multi-cohort study

OBJECTIVES: To examine the associations of life-course stressful life events (SLEs) with intrinsic capacity in older adults from the US, England and China. DESIGN: Prospective cohort study. SETTING AND PARTICIPANTS: A total of 6241 older adults from the US Health and Retirement Study (HRS), 2857 from the English Longitudinal Study on Ageing (ELSA), and 5829 the China Health and Retirement Longitudinal Study (CHARLS). MEASUREMENTS: Childhood and adulthood SLEs were self-reported by participants and were categorised into four groups: none, childhood only, adulthood only, and both. Intrinsic capacity consisted of five domains: locomotion, vitality, sensory, psychology and cognition. The level of each domain was converted into z-score by subtracting the mean and dividing the standard deviation. The composite z-score of intrinsic capacity referred to the mean of the z-scores of each domain. RESULTS: The mean (±standard deviation) age of the participants were 75.2 (±7.2), 70.5 (±7.5) and 67.5 (±6.1) years in HRS, ELSA and CHARLS. In three studies, there were 2672 (42.8%), 293 (10.3%) and 655 (11.2%) experiencing both childhood and adulthood SLEs, respectively. Older adults exhibited a decline in intrinsic capacity with increasing age. Compared to no SLEs, experiencing both childhood and adulthood SLEs was associated with significantly lower intrinsic capacity [β = -0.128 (95% CI = -0.159 to -0.097), relative risk (RR) = 1.25 (95% CI = 1.14 to 1.37) in HRS; β = -0.142 (95% CI = -0.189 to -0.095), RR = 1.28, (95% CI = 1.16-1.42) in ELSA; β = -0.156 (95% CI = -0.191 to -0.120), RR = 1.24 (95% CI = 1.16-1.33) in CHARLS]. CONCLUSION: Exposure to stressful life events, either in childhood or in adulthood or both, were associated with lower intrinsic capacity in late life. Individuals with SLEs during their life span should prioritised in prevention of functional decline and changing the environmental context and promoting social support can be a prominent strategy for reducing adulthood adversity.